I found nothing in the UPIA for CA to disallow this discretion.  16335 supports it:  

16335 a) In allocating receipts and disbursements to or between principal and income, and with respect to any other matter within the scope of this chapter, a fiduciary:

(1) Shall administer a trust or decedent's estate in accordance with the trust or the will, even if there is a different provision in this chapter.